Method of manufacturing electric discharge tubes



Aug. 27, 1940. o. BAIER 2,212,556

METHOD OF MANUFACTURING ELECTRIC DISCHARGE TUBES Filed Jan. 50, 1937 Patented Aug. 27, 1940 UNITED STATES PATENT OFFICE METHOD OF MANUFACTURING ELECTRIC DISCHARGE TUBES Application January 30, 1937, Serial No. 123,205 In Germany January 28, 1936 3 Claims.

Methods of producing and tooling ceramic materials of the kind adapted for use with electric devices, especially high frequency devices, have been improved in such a manner that discharge vessels and the like can be manufactured mainly from ceramic materials.

The invention relates to a novel method of manufacturing such tubes. More particularly, the invention is concerned with tubes of the kind wherein parts thereof are held together by glass seals or seals of another suitable material, and one of its objects is to produce such seals in a furnace in order to employ a nonoxidizing or reducing atmosphere and in this way to protect the electrodes from oxidizing.

Other objects and advantages will be understood from the following description, reference being had to the accompanying drawing in which Fig. 1 is a partially diagrammatic sectional view of an electron tube of the kind adapted to be manufactured by the novel method. Fig. 2 is a sectional view representing another kind of electron tube with which the invention is applicable. Fig. 3 is a partially diagrammatic sectional view illustrating a slight modification of the device shown in Fig. 1.

The tube shown in Fig. 1 has a vacuum vessel which is composed of a ceramic cylinder l, formed integral with an end wall or bottom 2 by any known method, and of a ceramic cover 3. Bottom 2 carries two conductors 4, 5. Two conductors 6, I are carried by cover 3. These conductors are fastened to bottom 2 or cover 3 by glass seals 20, 2!, 22, 23 and are connected to electrodes 34, 35, 36, 31 which are in this way supported by them. For instance, conductor 4 is joined to the anode 34 while conductor 5 is connected to a suppressor grid 35. Conductor 6 is secured to grid 36, and conductor 1 is connected to the cathode 31. Such electrodes are shown in dotted lines and in a purely diagrammatic manner, since they are immaterial to the invention. Cover 3 has a tubular extension 8 that serves for evacu-. ating the vessel in a well known manner. After such evacuation the vessel is sealed off at 3.

The manufacture of the tube is as follows.

The conductors 4, 5 are sealed into the bottom 2 while conductors 6, l are sealed into cover 3, this being done by means of the seals 20 to 23 which may consist of hard glass, for instance. The conductors are fastened or welded to the electrodes either before producing the seals or thereafter. In the case represented by way of example it is best to fasten them thereto prior to producing the seals 20 to 23 and then to proceed as follows. The conductors 4 to 1,.fixed to the electrodes 34 to 31, are inserted in bores of the parts 2, 3, whereupon the seals 20 to 23 are produced in order to fasten these conductors in such bores. The scaling is best effected in a furnace, the advantage being that a reducing atmosphere can be employed in order to prevent the electrodes from oxidizing. The two structures I, 2, 4, 5, 20, 2i and 6, I, 3, 22, 23 are then placed together, when the second melting operation has to be effected. This consists in producing the seal 10 by which the cover 3 and cylinder I are firmly held together. Preferably, this melting too is accomplished in a furnace in order to ensure a perfect result. In order however to avoid the seals 20 to 23 becoming soft, thus admitting of displacement of the electrodes, such second melting operation is effected by means of a material which is of a lower melting point than the sealing material at 20 to 23. While as stated hard glass or the like is suitable for the seals 20 to 23, so called soldering glass may be used for the seal Ill. The tube is then evacuated in a well known manner by means of a pump connected with the tubular extension 8 by the intermediary of a piece of glass tube inserted over extension 8. This piece of glass is sealed off after evacuation so as to form a glass seal 9, as is well known with devices of this kind. Such glass tube is preferably likewise of a hard glass. This is possible here since the sealing off is effected with the aid of a pointed flame so as to cause only a local heating. The remaining melting spots may be protected from the influence of heat.

In connection with the here described method gauges or other devices adapted to attain the highest degree of accuracy may be employed. The ceramic bodies may be so constructed that they are not subjected to mutual displacement during the time in which the several melting operations are effected. For instance, cover 3 may be provided with an annular groove adapted to receive the open end of cylinder I. The methods of tooling ceramic material have been so improved that accuracies of a fraction of one millimeter can be obtained. This is advantageous above all in the case of electron tubes made of a ceramic material, since material of this nature permits the desired proportions to be adhered to very closely. The novel method is therefore particularly suitable in the case of tubes intended for very short wave lengths, the inner dimensions of the tube being as predetermined.

In the construction shown in Fig. 2 the anode 34 is arranged to form part of the vacuum vesmaterial.

sel. This tube is of small dimensions while being intended for greater demands. The anode 34 has cooling ilns II and is preferably made of copper. two cylinders I2, I! and two covers l4, 3. The anode has an annular projection it .at each oi its face ends. In these projections the cylinders l2, I! are seated. Preferably, the projections l8 are shrunk onto these cylinders.

Electrode leads 4, are illustrated but the electrodes provided in addition to the anode 34 are not shown in Fig. 2 as their structure is not material to the practising of the invention.

The parts represented in Fig. 2 are rigidly interconnected by annular seals l0, l8, l1, l8. which may be done by tubular pieces of glass, for instance, which are inserted over the parts to be fastened to each other and are then caused in a furnace to melt.

The seals l'l, i8 are produced in a first melting operation by means of a hard glass or similar The seals l0, it are made in a second operation and consist of a material having a lower melting point than the material of which seals l1, l8 are made.

In the construction represented in Figs. 1 and 2 the tubular extension 8 is made in one with cover 3. Tubes of this kind being very small, however, extension 8 and cover 3 are easy to in- Jure in the course of manufacture. Therefore,

as shown in Fig. 3, the tubular extension 8 may be fixed in a recess o? he cover 3 by means of a seal 24 whose melting point is lower than that of The vacuum vessel further consists of the seals 20 to 28. The seals i0 and 24 may thus be produced in the same operation. In other respects the construction represented in Fig. 3.

is the same as that shown in Fla. 1.

What is claimed is:

i. The method of manufacturing a discharge tube having envelope part of ceramic material and at least one portion of metal, which comprises Joining the metal portion to a ceramic part by one melting operation using a material having a high melting point, such as hard glass, and subsequently Joining said one ceramic portion to another ceramic portion by a melting operation using another material having a lower melting point, such as soft glass.

2. ,A method in accordance with claim 1 wherein the Joining operation is carried out in a reducing atmosphere.

3. The method of manufacturing a discharge tube having portions of ceramic material, forming at least a part of the envelope tube, and parts of metal including a member extending through a bore in one of said portions of ceramic material, which comprises: sealing'the metallic member in said bore with a material having a high melting point such as hard glass, then attaching an electrode to said member, and finally Joining the portions of ceramic material together by a melting operation using a sealing material having a relatively low melting point,

such as soft glass.

O'I'I'O BAIER. 

